Strange power problems with the Fit PC 2

First, I’d like to thank George Hunt for setting up this blog, and letting me post OLPC XS School Server issues here. Thank you.

I have a Fit PC 2 that I’ve used for testing XS 0.6 and XS 0.7 builds. The box is a neat, fanless device that pulls approximately 15 watts on the AC end of the power brick. It does run hot, but a heat sink can solve that problem, and clever mounting with good airflow can solve that problem in the field. I like the fact that this box has a 12V DC input. In tests, we found that the Fit PC2 could support a network of 150 to 175 XOs quite easily.

A few days ago, my unit started to behave strangely. It would not boot up headless. However, if I plugged in a HDMI cable and plugged it into a powered device (such as a TV) on the other end, it would boot up fine!

This wasn’t some accidental BIOS setting that I had changed. It turned out that the power socket that was soldered onto the board had plenty of headroom to wiggle, and given that the power plug would always pull downwards, the continuous pressure had broken off one of the 12V contacts inside. So, it was getting one of the polarities, and perhaps the HDMI cable provided the other path for it to boot, but without the HDMI cable, plugged into a powered device, the box would not boot up.

I pulled it apart, re-soldered the contacts, and filled in the extra headroom with a stack of folded paper (any other suggestions for filler material?). Now, when the plug pulls on the socket, there is no wiggle room, so I hope it will hold.

If you plan on using a Fit PC2 in the field, watch out for this behavior!

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About sv3rma

http://olpcsf.org http://bhagmalpur.wordpress.com http://olpcjamaica.org.jm http://olpctuva.wordpress.com
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